What is the purpose of Underlay?

The purpose of underlay for timber flooring is mainly related to the below reasons:
- Underlay has acoustic deafening properties
- The softness of the underlay creates a soft backing for a softer step, if the timber was directly on concrete it would be very hard under the foot
- It will help with creating a moisture barrier between concrete and timber, this is required because the concrete contains moisture in it that can affect timber
- The underlay helps absorb any grit and minor slab deviations
- Used as a thermal break

 

 Different types of Installs
- In a floating floorboard, if you have an acoustic underlay (which is a roll), it is not required to glue the flooring to the underlay
- In a glued floor, you seal the concrete, then use glue to level the slab (the glue is used for the same purposes as the underlay), but the timber floorboard is stuck onto it

 

Also, note separate from the install type is the type of flooring interlocking system. There is:
- Secret nailing (typically only used for hardwood flooring)
- Exposed nailing (typically only used for hardwood flooring)
- Clip lock  (no glue required)
- Tongue and groove (glue is required)